11 Knowing, therefore, the terror of the Lord, we persuade men; but we are well known to God, and I also trust are well known in your consciences.
12 For we do not commend ourselves again to you, but give you opportunity to boast on our behalf, that you may have an answer for those who boast in appearance and not in heart.
13 For if we are beside ourselves, it is for God; or if we are of sound mind, it is for you.
terror (v.11) = fear, reverence, respect
commend (v.12) = lit. “stand together,” referring to facts “lining up” with each other to support something
boast (v.12) = glory, the grounds for glorying
appearance (v.12) = surface
beside ourselves (v.13) = astonished, amazed, overwhelmed, lit. to “displace”
Knowing therefore the fear of the Lord, we are persuading men [of our sincerity and integrity], but to God we have been openly shown [as to our character], and I am hoping that we have been openly shown to be what we are in your consciences. We are not again commending ourselves to you, but [are writing these things] as giving you a base of operations from which to glory about us, in order that you may be having this matter of glorying with which to answer those who are glorying in outward appearance and not in the heart [the inner man]. For, whether we were out of our mind, it was with respect to God; whether we are of sober mind, it is with respect to you. — Wuest, pages 423-424.
The Apostle knew that the purity of his doctrine and of his motives were manifest to God, and he hoped that they were manifest also to the Corinthian conscience (v.11). he did not again commend himself to them but gave material to those in Corinth who were loyal to the Gospel that they might boast of him in opposition to those with whom carnal endowments were everything and sincerity of heart nothing (v.12). If he appeared to have been mad it was for God’s glory, but if now accounted to be in his right mind it was for their benefit (v.13). — Williams, page 902
In the first chapters of 2 Corinthians Paul has been defending his God-given apostleship because some among them had questioned this. They had said in effect. “He’s not a legitimate apostle. Ask him if he is one of the twelve Christ named and see if he dares to answer that!” …
Again and again, Paul magnifies his office [for example, “For I speak to you Gentiles, inasmuch as I am the apostle of the Gentiles; I magnify mine office” (Romans 11:13)], and this was necessary, lest the whole Church be plunged back into the bondage of legalistic religion. — Stam, page 112.
[To understand 2 Corinthians 5:13, we must look at the context.]
The Corinthians as a church were badly backslidden. This is evident, not only from verses 10-11, but from Paul’s first letter to them, for 1 Corinthians is an epistle of rebuke.
They—Paul too—were “all to appear before the Judgment Seat of Christ, that every one may receive the things done in his body … whether it be good or bad [Lit. worthless]”: a frightening prospect for backslidden believers.
“Knowing therefore the terror of the Lord,” he says, he “persuaded” men, realizing that he himself was “manifest unto God,” and trusting that he and his way of life would be “made manifest” to their consciences.